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<span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
  name<span class="token operator">:</span> <span class="token string">'keep-alive'</span><span class="token punctuation">,</span>
  abstract<span class="token operator">:</span> <span class="token boolean">true</span><span class="token punctuation">,</span> <span class="token comment">// 判断当前组件虚拟dom是否渲染成真实dom的关键</span>
  props<span class="token operator">:</span> <span class="token punctuation">{</span>
      include<span class="token operator">:</span> patternTypes<span class="token punctuation">,</span> <span class="token comment">// 缓存白名单</span>
      exclude<span class="token operator">:</span> patternTypes<span class="token punctuation">,</span> <span class="token comment">// 缓存黑名单</span>
      max<span class="token operator">:</span> <span class="token punctuation">[</span>String<span class="token punctuation">,</span> Number<span class="token punctuation">]</span> <span class="token comment">// 缓存的组件</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token function">created</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
     <span class="token keyword">this</span><span class="token punctuation">.</span>cache <span class="token operator">=</span> Object<span class="token punctuation">.</span><span class="token function">create</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token comment">// 缓存虚拟dom</span>
     <span class="token keyword">this</span><span class="token punctuation">.</span>keys <span class="token operator">=</span> <span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token comment">// 缓存的虚拟dom的键集合</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token comment">/* destroyed钩子中销毁所有cache中的组件实例 */</span>
  <span class="token function">destroyed</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">const</span> key <span class="token keyword">in</span> <span class="token keyword">this</span><span class="token punctuation">.</span>cache<span class="token punctuation">)</span> <span class="token punctuation">{</span>
       <span class="token comment">// 删除所有的缓存</span>
       <span class="token function">pruneCacheEntry</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>cache<span class="token punctuation">,</span> key<span class="token punctuation">,</span> <span class="token keyword">this</span><span class="token punctuation">.</span>keys<span class="token punctuation">)</span>
    <span class="token punctuation">}</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span>
 <span class="token function">mounted</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
   <span class="token comment">// 实时监听黑白名单的变动</span>
   <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">$watch</span><span class="token punctuation">(</span><span class="token string">'include'</span><span class="token punctuation">,</span> <span class="token parameter">val</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
       <span class="token function">pruneCache</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">,</span> <span class="token parameter">name</span> <span class="token operator">=&gt;</span> <span class="token function">matched</span><span class="token punctuation">(</span>val<span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span><span class="token punctuation">)</span>
   <span class="token keyword">this</span><span class="token punctuation">.</span><span class="token function">$watch</span><span class="token punctuation">(</span><span class="token string">'exclude'</span><span class="token punctuation">,</span> <span class="token parameter">val</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
       <span class="token function">pruneCache</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">,</span> <span class="token parameter">name</span> <span class="token operator">=&gt;</span> <span class="token operator">!</span><span class="token function">matches</span><span class="token punctuation">(</span>val<span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">)</span>
   <span class="token punctuation">}</span><span class="token punctuation">)</span>
 <span class="token punctuation">}</span><span class="token punctuation">,</span>

 <span class="token function">render</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">/* 得到slot插槽中的第一个组件 */</span>
    <span class="token keyword">const</span> vnode<span class="token operator">:</span> VNode <span class="token operator">=</span> <span class="token function">getFirstComponentChild</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>$slots<span class="token punctuation">.</span>default<span class="token punctuation">)</span>
    <span class="token keyword">const</span> componentOptions<span class="token operator">:</span> <span class="token operator">?</span>VNodeComponentOptions <span class="token operator">=</span> vnode <span class="token operator">&amp;&amp;</span> vnode<span class="token punctuation">.</span>componentOptions
    <span class="token keyword">if</span> <span class="token punctuation">(</span>componentOptions<span class="token punctuation">)</span> <span class="token punctuation">{</span>

    <span class="token punctuation">}</span>
    <span class="token keyword">return</span> vnode
 <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
</code></pre></div><h4 id="destroyed-生命周期"><a href="#destroyed-生命周期" class="header-anchor">#</a> destroyed 生命周期</h4> <ul><li>不是简单的 <code>this.cache=null</code>, 而是遍历销毁所有的缓存组件</li> <li>内部会调用<code>vm.$destroy()</code>, 完全的销毁一个实例，清理它与其他实例的连接，解绑它的全部指令和事件监听器。</li> <li>会触发各个缓存组件的<code>beforeDestroy和destroyed</code>的钩子。</li></ul> <h3 id="被缓存组件的生命周期"><a href="#被缓存组件的生命周期" class="header-anchor">#</a> 被缓存组件的生命周期</h3> <ul><li><p>第一次渲染就是 正常的生命周期，然后多一个 <code>activated</code>和<code>deactivated</code>钩子函数。</p></li> <li><p>保存的是 VNode</p></li> <li><p>通过 cache对象保存</p></li> <li><p><code>render</code>方法通过 $slots.default 来缓存对应的<code>vnode</code>虚拟Dom节点</p></li></ul></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">最后一次修改时间:</span> <span class="time">9/28/2020, 11:37:23 AM</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev">
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